High level of tumour protein p53-induced nuclear protein 1 (TP53INP1) expression in anaplastic carcinoma of the thyroid.

Tumour protein p53-induced nuclear protein 1 (TP531NP1) is a stress-induced protein and plays a role in cell cycle arrest and p53-mediated apoptosis. In this study, we investigated TP531NP1 expression in human thyroid neoplasms. We immunohistochemically investigated TP531NP1 in 197 cases of various thyroid neoplasms. Normal follicles did not express TP531NP1. All 39 (20 minimally invasive and 19 widely invasive) follicular carcinomas and 20 adenomas were negative for or expressed only low levels of TP531NP1 except for one widely invasive follicular carcinoma. Of 100 papillary carcinomas, only four (4%) expressed high levels of TP531NP1, and the remaining 96 (96%) were classified into the low group. There were no significant relationships between TP531NP1 expression and clinicopathological features of papillary carcinoma. However, 36 of the 38 (94.7%) anaplastic carcinomas expressed high levels of TP531NP1 and the incidence was significantly higher (p<0.0001) than that in other neoplasms. These findings suggest that TP531NP1 plays a significant role in the progression of anaplastic carcinoma or contributes to anaplastic transformation from papillary or follicular carcinoma, which is in sharp contrast to findings in previous in vitro and in vivo studies.